Note 5 - Warrants - Warrants Outstanding (Details) - $ / shares		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Aug. 31, 2023	Jun. 30, 2023	Sep. 30, 2022	Jun. 30, 2022
Balance outstanding (in shares)		1,372,157	220,192
Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)		$ 23.55
Warrants Issued in February 2018 [Member]
Balance outstanding (in shares)	[1]	0	25,264
Warrants Issued in February 2018 [Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)	[1]	$ 0
Warrants Issued in June 2018 [Member]
Balance outstanding (in shares)	[1],[2]	0	8,256
Warrants Issued in June 2018 [Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)	[1],[2]	$ 0
Warrants Issued in March 2019 [Member]
Balance outstanding (in shares)	[1]	17,568	17,568
Balance outstanding, remaining contractual life (Year)	[1]	2 months 12 days
Warrants Issued in March 2019 [Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)	[1]	$ 99
Warrants Issued in April 2019 [Member]
Balance outstanding (in shares)	[1]	58,334	58,334
Balance outstanding, remaining contractual life (Year)	[1]	3 months 18 days
Warrants Issued in April 2019 [Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)	[1]	$ 157.5
Warrants Issued in February 2020 [Member]
Balance outstanding (in shares)	[1]	67,667	67,667
Balance outstanding, remaining contractual life (Year)	[1]	1 year 7 months 6 days
Warrants Issued in February 2020 [Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)	[1]	$ 94.5
Warrants Issued in December 2023 [Member]
Balance outstanding (in shares)	[1]	939,312
Balance outstanding, warrant exercise price (in dollars per share)	[1]	$ 9.6
Balance outstanding, remaining contractual life (Year)	[1]	5 years
Warrants Issued in December 2023 [Member] | Weighted Average [Member]
Balance outstanding (in shares)	[1]		0
Liability Classified Warrants [Member]
Balance outstanding (in shares)		1,082,881	177,089
Balance outstanding, remaining contractual life (Year)		5 years 1 month 6 days	1 year 8 months 12 days
Liability Classified Warrants [Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)		$ 24.3	$ 142.35
Warrants Issued in April 2020 for Consulting [Member]
Balance outstanding (in shares)		1,112	1,112
Balance outstanding, remaining contractual life (Year)		1 year 3 months 18 days
Warrants Issued in April 2020 for Consulting [Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)		$ 102.6
Warrants Issued in December 2020 for Consulting [Member]
Balance outstanding (in shares)		556	556
Balance outstanding, remaining contractual life (Year)		2 years
Warrants Issued in December 2020 for Consulting [Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)		$ 70.8
Warrant Issued in April 2021 for Consulting [Member]
Balance outstanding (in shares)		4,767	4,767
Balance outstanding, remaining contractual life (Year)		2 years 3 months 18 days
Warrant Issued in April 2021 for Consulting [Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)		$ 54.45
Warrant Issued in August 2021 for Consulting [Member]
Balance outstanding (in shares)		16,667	16,667
Balance outstanding, remaining contractual life (Year)		7 years 7 months 6 days
Warrant Issued in August 2021 for Consulting [Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)		$ 46.2
Warrants Issued in June 2022 for Consulting [Member]
Balance outstanding (in shares)		3,334	3,334
Balance outstanding, remaining contractual life (Year)		8 years 6 months
Warrants Issued in June 2022 for Consulting [Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)		$ 22.35
Warrant Issued in September 2022 for Consulting [Member]
Balance outstanding (in shares)		16,667	16,667
Balance outstanding, remaining contractual life (Year)		8 years 8 months 12 days
Warrant Issued in September 2022 for Consulting [Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)		$ 18.6
Warrants Issued in June 2023 for Consulting [Member]
Balance outstanding (in shares)		10,000	0
Balance outstanding, remaining contractual life (Year)		9 years 6 months
Warrants Issued in June 2023 for Consulting [Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)		$ 9
Warrants Issued in August 2023 for Consulting [Member]
Balance outstanding (in shares)		6,667	0
Balance outstanding, remaining contractual life (Year)		4 years 7 months 6 days
Warrants Issued in August 2023 for Consulting [Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)		$ 9.3
Pre-funded Warrants Member Issued In Connection With The 2023 Securities Purchase Agreement[Member]
Balance outstanding (in shares)		229,506	0
Balance outstanding, warrant exercise price (in dollars per share)		$ 0.001
Balance outstanding, remaining contractual life (Year)		5 years
Pre-funded Warrants Member Issued In Connection With The 2023 Securities Purchase Agreement[Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)		$ 0.001
Equity Classified Warrants [Member]
Balance outstanding (in shares)		289,276	43,103
Balance outstanding, warrant exercise price (in dollars per share)				$ 9.3	$ 9	$ 18.6	$ 22.35
Equity Classified Warrants [Member] | Weighted Average [Member]
Balance outstanding, warrant exercise price (in dollars per share)		$ 6

[1] If the Company subdivides (by any stock split, stock dividend, recapitalization or otherwise) its outstanding shares of its common stock into a smaller number of shares, the warrant exercise price is proportionately reduced and the number of shares under outstanding warrants is proportionately increased. Additionally, if the Company combines (by combination, reverse stock split or otherwise) its outstanding shares of common stock into a smaller number of shares, the warrant exercise price is proportionately increased and the number of shares under outstanding warrants is proportionately decreased. Also, the Company may voluntarily reduce the warrant exercise price for its warrants issued in March 2019.

[2] Taking into account the reverse stock splits we have completed, includes warrants to purchase 7,892 shares at an exercise price of $181.80, expiring December 22, 2023, and warrants to purchase 365 shares at an exercise price of $208.80, expiring June 21, 2023.